In the past, a quick-time file format (referred to hereafter simply as a QT format) was used in a broader range of applications as a file format for multimedia.
In accordance with the QT format, real data including moving pictures, still pictures and sound is divided into blocks. In addition, management information used for managing the real data is also divided into blocks separated from the blocks of the real data. In the following description, blocks of the management information and the real data are each referred to as an atom. Moreover, atoms of the real data and the management information are further divided into sub-blocks to form a hierarchical structure. In the case of the real data, a smallest management unit is referred to as a sample, and one sample or a plurality of samples forms a chunk, which is used as an upper-level management unit. Then, in the case of a file created from blocks as a file conforming to the QT format, considering convenience of processing, normally, one frame serving as a display unit or a GOP (Group of Pictures) is set in one sample as disclosed in a document such as Japanese Patent Laid-Open No. 2001-94933.
In general, a file having a QT format includes atoms of two different types, that is to say, a movie data atom of collected real data and a movie atom of collected management information.
By the way, in addition to the same recording method as the method for the QT format, a recording method for the so-called fragment movie format is applied as a recording method for the ISO base media file format (MPEG-4 part 12) taking the QT format as a base to apparatus with few resources and apparatus for which it is feared that the power supply thereof is down in the course of a recording process.
For the reason described above, the real data of an ISO base media file containing a fragment movie is segmented into a plurality of blocks each having a predetermined size in the progressing direction along the time axis as shown in FIG. 1. In the figure, the blocks of the real data are each shown as a block corresponding to one of a plurality of movie data atoms mdat0, mdat1, mdat2 and so on. In the following description, the ISO base media file is also referred to as a fragment movie file. The fragment movie file also includes a movie atom moov, associated with the movie data atom mdat0 serving as the first atom in the series of aforementioned movie data atoms mdat0, mdat1, mdat2 and so on. The movie atom moov has the same atom structure as the ordinary QT movie file. The movie atom moov is formed as an atom referring to the movie data atom mdat0 as shown by an uppermost arrow in the figure so as to allow video data allocated to the movie data atom mdat0 as real data to be reproduced. It is to be noted that the first movie data atom mdat0 is also known as an initial moov. Thus, in the following description, the first movie data atom mdat0 is also referred to as an initial moov atom.
In addition, the fragment movie file also includes an atom moof containing management information associated with each of the movie data atoms mdat1, mdat2 and so on. As shown in the figure, the atoms moof each containing management information are denoted by reference notations moof1, moof2 and so on. In the following description, the atoms moof1, moof2 and so on are each referred to as a moof atom. The moof atoms moof1, moof2 and so on are formed as atoms referring to their respective movie data atoms mdat1, mdat2 and so on respectively as shown by subsequent arrows in the figure so as to allow pieces of video data allocated to the movie data atoms mdat1, mdat2 and so on as pieces of real data to be reproduced.
Thus, while the movie data atoms mdat0, mdat1, mdat2 and so on are being stored sequentially in a created fragment movie file in a recording process, the initial moov atom associated with mdat0 as well as the moof atoms moof1, moof2 and so on associated with the movie data atoms mdat1, mdat2 and so on respectively are also stored on the created file sequentially as well. Thus, even an apparatus having few resources is capable of recording a fragment movie file with a large size onto a recording medium. In addition, even if the power supply thereof is down in the course of a recording process, video data up to a portion corresponding to the down event can be recorded in a reproducible state onto the recording medium.
In addition, in a fragment movie file, the initial moov atom has a structure of management information associated with the video data of the movie data atom mdat0. The management information set in the initial moov is set for chunks of the movie data atom mdat0 and samples of each of the chunks. The chunks and samples are each used as a management unit of real data much like the movie atom of the ordinary QT movie file. On the other hand, the moof atoms moof1, moof2 and so on are each provided with a structure different from the initial moov atom with an objective to reduce the amount of management information accommodated in the moof atom. That is to say, with every default setting in each of the moof atoms moof1, moof2 and so on as a reference, the moof atoms moof1, moof2 and so on can each have a structure of condensed set management information related to the movie data atoms mdat1, mdat2 and so on respectively for each sample.
Thus, in processing to reproduce a fragment movie file, it is necessary to switch the reproduction processing from the initial moov atom to one of the moof atoms moof1, moof2 and so on. As a result, the fragment movie file raises a problem of complicated processing carried out at a reproduction time.